If potted lavender leaves are turning yellow it’s most likely a sign of stress due to excess nitrogen in the soil. Lavenders require low to medium fertility soil. If nitrogen fertilizer is added or materials such as manure or enriched compost are used lavender leaves will turn yellow and the plant will often grow leggy with fewer blooms.
Yellow leaves could also indicate overwatering or lavender that is not in an area with good airflow (lavenders dislike still air) or perhaps the soil is too acidic.
Lavenders are native to arid Southern Europe, where they thrive in coastal areas with alkaline, low to medium fertility, sandy soils that do not retain moisture and with little rainfall.
To prevent lavender leaves from turning yellow it is important to recreate some of their natural conditions so that they stay healthy and display blooms.
Keep reading to learn why your potted lavender leaves are turning yellow and how to fix the problem…
1. Yellow Leaves due to Nutrient rich Soil
Yellow leaves are often a sign that the soil mix is too high in nitrogen. Lavenders grow best in a low to medium fertility potting mix. If there is too much nitrogen in the soil then the lavenders will turn yellow and produce fewer flowers.
If you have planted your potted lavenders with…
- Manure, or
- Enriched compost
…or something similar, then the nutrient rich soil mix is contrary to the low fertility conditions that lavenders require which results in yellow leaves.
Other signs of stress are fewer blooms in the summer and leggy, untidy growth.
The solution is to amend the soil before planting.
The best soil mix for lavenders is well draining (to prevent root rot) and contains roughly 1/3 of horticultural sand or grit with 2/3’s ordinary potting soil which can be bought for any good garden center.
(Read more in my article, for how to create the optimal potting soil for lavenders in pots and containers).
The sandy soil mix recreates the sandy conditions that lavenders grow to their best in countries like Spain, France, and Portugal.
With a low to medium fertility soil mix lavenders will grow properly, and display more flowers and the foliage should be green with a strong aroma.
It may take a few weeks for lavenders with yellow leaves to recover when they are transferred to a new potting mix so you have to be patient but it should recover.
2. Leaves Turning Yellow Because of Fertilizer
This is a common mistake that a lot of gardeners make. As lavenders are adapted to low to medium fertility soils they do not require additional fertilizer.
Fertilizing lavenders will have the same effect (if not worse) than planting lavenders in nutrient-rich soil.
The first sign of stress from additional fertilizer is that the leaves turn yellow, and fewer blooms in the summer as well as a less intense aroma and an untidy appearance.
Once fertilizer has been applied the only thing you can do is to replace the potting soil with a sandy or gritty potting mix and replant the lavender.
When amending the new soil, use horticultural sand or grit as this sand has a larger particle size to create a more porous soil that allows for good drainage and root respiration.
3. Root Rot Because of Overwatering
Lavenders are affected by very few diseases, however, root rot can be a problem because of:
- Watering too frequently
- Slow draining soil
- Pots without drainage holes in the base
Lavenders in pots require a generous soak once every two or three weeks. If you are watering more frequently than this then you are probably overwatering the lavender.
(Read my article on how often to water lavender)
Lavenders are drought-resistant, heat-tolerant plants, that prefer the soil to dry out between bouts of watering.
Soil that is consistently moist will promote the conditions for the fungal disease root rot which can turn the lavender leaves, yellow/brown and often cause a drooping appearance.
Even if you are not watering your lavender frequently, it may be the case that the soil is too rich and retains a lot of moisture. It is always important to add a generous portion of sand or grit to the potting mix before planting to ensure good soil drainage.
With sandy soil, there is much less risk of your lavender developing root rot even if the plant is overwatered or receives a lot of rainfall.
The solution is to remove the lavender from the soil and snip off any roots that look yellow and rotten with a sterile pair of pruners, leaving only healthy, normal roots.
Replant the lavender in new potting mix with plenty of sand or grit and leave it to dry out for two weeks.
The advantage of potted lavender is that you can move it to a sheltered location, out of rainfall to give the roots and soil a chance to dry out.
After two weeks, water the lavender once every two or three weeks until the Fall (do not water lavender in Winter as it is in a state of dormancy and will attain all the moisture it requires if left outdoors).
Lavenders do not always recover from severe root rot, but if you act quickly there is a good chance the plant will recover properly.
4. Inappropriate Pot for Lavenders
It is possible that lavender leaves could turn yellow as a sign of stress if they are planted in a pot that is too small, leaving them root-bound.
Plant lavenders in a pot that is at least 12-16 inches across even if it is a smaller variety such as Lavandula angustifolia ‘Hidcote Superior’ or Lavandula stoechas ‘Anouk’.
This size pot will ensure the lavender root system has enough space to establish and the pot has the capacity for soil with enough moisture and access to nutrients.
A larger pot also means that there is more soil to insulate the roots in Winter.
Read my article to learn more, about choosing the right pot for lavenders.
Another potential problem is pots without drainage holes in the base or the use of a plate to catch water trickling out of the base of the pot.
If excess water can not easily drain out the base of the pot then the soil will be too moist for the lavender roots. This will cause root rot and the lavender’s leaves will turn yellow/brown with an overall drooping appearance.
5. Soil pH
Lavenders can tolerate some mild soil acidity but prefer to grow in soils that are pH neutral or alkaline which is anywhere from pH 6.5 which is acidic to pH 8 which is alkaline. (Read my article for how to measure soil pH, for lavenders).
Lavenders that are planted in an acidic soil mix can struggle to uptake nutrients which causes yellow leaves and stunted growth.
Avoid using ericaceous (acidic) compost and plant lavenders in normal potting soil. Adding a tablespoon of horticultural lime (available from garden centers or online) or half a cup of wood ash (both are alkaline) will ensure that the lavender soil mix is within the optimal range.
Remove lavenders from the soil urgently if you suspect acidic soil is the problem and replant them in new soil with some lime to give the lavender the best chance of recovery.
(Read my article, on how to grow lavenders in pots and containers).
- A potted lavender with yellow leaves is usually a sign that there is too much nitrogen in the soil due to fertilizer or soil that is too nutrient rich (Lavenders prefer low to medium fertility soil).
- Overwatering and slow-draining soils can cause fungal disease which causes lavender leaves to turn yellow or brown with a drooping appearance. Lavenders are drought-resistant plants that only require watering very infrequently when established. Plant lavenders in sandy soil to improve drainage.
- It is important to choose the right pot for lavenders. A root-bound lavender may have yellow leaves and stunted growth as a sign of stress. Lavenders require pots with drainage holes in the base so that excess water escapes, to prevent root rot.
- Lavenders prefer alkaline soils and do not grow very well in acidic soil conditions. The lavender leaves may turn yellow and with poor or stunted growth. Replant the lavender in a pot with some horticultural lime or wood ash (which are both alkaline) to ensure the soil is in the correct range for growing lavender.
- To grow healthy lavenders and avoid leaves turning yellow, try to replicate the conditions of the lavender native environment in the Mediterranean, with sandy soils, infrequent watering, and full sun.